Conventionally, in order to get a better quality of an image, when an ultrasonic diagnose is performed by use of B-type ultrasonic imaging technology, an operator of ultrasonic imaging system has to adjust TGC (Time Gain Compensation), Gain (total gain), dynamic range etc. These adjustments result in an elongated time for the diagnosis. This problem is usually solved by a so called “one button for optimizing B type images” technique. The “one button for optimizing B type images (i.e. black and white images)” technique aims to simplify the adjustment of TGC, Gain and dynamic range. The user is only required to press one button, and then the ultrasonic system can automatically analyze the most appropriate TGC, Gain and other parameters related to imaging procedure and make those appropriate parameters valid. Accordingly, a better image is obtained, and the efficiency as well as accuracy of the diagnosis are effectively enhanced. This technique is referred as “one button optimization” or “automatic image equilibrium”.
Most of the one button optimization (or automatic image equilibrium) techniques are based on the analysis of the change of gray level value of the image in the direction of depth. An appropriate TGC curve and Gain are calculated based on the analysis. For example, U.S. Pat. Nos. 6,743,174B2, 5,579,768, 6,120,446 and 6,102,859 provide some approaches to implement the technique. There are many different ways to analyze the change of gray-level, and the suppression of noise is also taken into considered in the procedure of the analysis. In particular, U.S. Pat. No. 6,743,174B2 proposes a method to automatically optimize the dynamic range.
In U.S. Pat. No. 6,743,174B2, it is assumed that the gray level is changed evenly and monotonically in the direction of depth, and it can be fitted by a straight line. This assumption is against most of the practical situations. Moreover, since average value and median value of gray level are used in this method to adjust dynamic range, it can not achieve a good result. In the methods proposed by U.S. Pat. Nos. 5,579,768 and 6,102,859, B type images are evenly divided along the radial direction and tangent direction of the probe. The average gray level of each divided area is taken into account in the procedure for analyzing the change of gray level. Consequently, this approach may lead to inaccuracies in the result of the analysis. Besides, since homogeneous soft tissue sub-areas, noise sub-areas and structural tissue sub-areas etc, which indicate different gray levels, are included in the captured B type image, the approach for evenly dividing the sub-area is not appropriate for the analysis of the gray level of whole image.